Engines operate by providing heat, oxygen, and fuel in the proper combination (air/fuel ratio) to produce contained combustion within the engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as a stoichiometric mixture, often abbreviated to stoich. Deviating from stoich has ramifications on the emissions, efficiency, and performance produced thereby. In direct injection engines, electrically controlled injectors deliver fuel directly into the cylinders. While all the injectors may be supplied fuel by a common high pressure rail, such injectors provide the ability to precisely control both the amount and the time instant the fuel is delivered on a cylinder-by-cylinder basis. Air (charge) provided to a cylinder is at least partially a function of the position and movement of an intake valve of the engine. Charge provided to a cylinder is further a function of valve settings. In an effort to get more oxygen molecules in a cylinder, turbochargers are used. Turbocharging machinery is well-known and commonly used in the internal combustion engine industry to pressurize intake air entering the engine combustion chambers and thereby increase the efficiency and power output of the engine.
Whereas the electronic fuel injectors allow precise metering that is readily adjustable during operation and can be adjusted on a cylinder-by-cylinder basis at a speed that is appropriate for the number of injection events per second, providing charge flow is largely a mechanical process that is not as conducive to quick changes or to cylinder-by-cylinder customization.
Accordingly, changes to operation of a cylinder are commonly effected by altering the fueling profile thereof. Any changes made to the charge flow are able to be implemented much slower than fueling changes. If a cylinder is experiencing a different charge flow than other cylinders, the system either risks deviating from stoich, or (if the system compensates by altering the fueling command for the deviant cylinder) risks having a power output imbalance between the cylinders (if no further compensation is applied).
What is therefore needed is a system for allowing effective change in charge flow having a speed of change closer to that achievable with fueling and having the ability to be customized cylinder-by-cylinder.